Power line communication (PLC), also called mains communication, power line transmission or power line telecommunication (PLT), broadband power line (BPL), power band or power line networking (PLN) is a term describing several different systems for using power distribution wires for simultaneous distribution of data. A carrier can communicate voice and data by superimposing an analog signal of a standard 50 or 60 Hz alternating current (AC). For indoor applications, PLC equipment can use household electrical power wiring as a transmission medium. This is a technique used e.g. for home networking or in home automation for remote control of lighting and appliances without installation of additional wiring.
In standard PLC systems the signals are transmitted and received in a differential mode (DM). Differential mode signaling is a method of transmitting information over pairs of wires. At DM signaling one wire carries a signal and the other wire carries the inverse of the signal, so that the sum of the voltages to ground on the two wires is always assumed to be zero. PLC modems therefore inject a DM signal between a neutral line and the phase line of an outlet of the power line network of the household for communication purposes. Another PLC modem can receive such DM signals at another outlet and use the DM signal for controlling an appliance associated with the receiving PLC modem.
However, at in-house power line grids, there are asymmetric elements between the phase line and the neutral line, like e.g. an open light switch, the current bar and the fuse cabinet, branches, etc. At these asymmetric elements, the DM signals injected by PLC modems are converted to common mode (CM) signals. Multiple input-multiple output PLC modems can use different channels, in particular also common mode signals, in order to enhance the coverage of PLC systems.
Fixed radio broadcasting or other external transmissions might have interferences with power line communication. PLC modems might have fixed notch filters for amateur radio bands. Concepts of dynamic or smart notching, e.g. like specified in ETSI TS 102 578, enables PLC modems to depict an ingress of fixed radio broadcast stations. The frequency where radio stations have been detected should be omitted by power line communication. In order to realize such an omission in a PLC transmitter, adaptive notch filters for suppressing a transmission signal in a predetermined frequency band might be used. There is a need of further improvements in detecting an ingress of short wave radio signals.